From b13fc7fa257018cdf2c847b8aace0b386e38d166 Mon Sep 17 00:00:00 2001 From: RCE Date: Sun, 20 Apr 2014 11:17:26 +0200 Subject: [PATCH 1/1] Ajout de la partie d adaptation du programme a Siimgrid --- hpcc.tex | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/hpcc.tex b/hpcc.tex index 014366c..3d861f3 100644 --- a/hpcc.tex +++ b/hpcc.tex @@ -320,7 +320,20 @@ where $\MI$ is the maximum number of outer iterations and $\epsilon$ is the tole \LZK{Description du processus d'adaptation de l'algo multisplitting à SimGrid} %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% - +We did not encounter major blocking problems when adapting the multisplitting algorithm previously described to a simulation environment like SIMGRID unless some code +debugging. Indeed, apart from the review of the program sequence for asynchronous exchanges between the six neighbors of each point in a submatrix within a cluster or +between clusters, the algorithm was executed successfully with SMPI and provided identical outputs as those obtained with direct execution under MPI. In synchronous +mode, the execution of the program raised no particular issue but in asynchronous mode, the review of the sequence of MPI\_Isend, MPI\_Irecv and MPI\_waitall instructions +and with the addition of the primitive MPI\_Test was needed to avoid a memory fault due to an infinite loop resulting from the non- convergence of the algorithm. Note here that the use of SMPI +functions optimizer for memory footprint and CPU usage is not recommended knowing that one wants to get real results by simulation. +As mentioned, upon this adaptation, the algorithm is executed as in the real life in the simulated environment after the following minor changes. First, all declared +global variables have been moved to local variables for each subroutine. In fact, global variables generate side effects arising from the concurrent access of +shared memory used by threads simulating each computing units in the Simgrid architecture. Second, the alignment of certain types of variables such as "long int" had +also to be reviewed. Finally, some compilation errors on MPI\_waitall and MPI\_Finalise primitives have been fixed with the latest version of Simgrid. +In total, the initial MPI program running on the simulation environment SMPI gave after a very simple adaptation the same results as those obtained in a real +environment. We have tested in synchronous mode with a simulated platform starting from a modest 2 or 3 clusters grid to a larger configuration like simulating +Grid5000 with more than 1500 hosts with 5000 cores [?]. Once the code debugging and adaptation were complete, the next section shows our methodology and experimental +results. -- 2.39.5